How can I wrap or scroll text inside a GtkLabel to keep the width?

[Guenther Meyer <d s e sordidmusic com>]

hi,

I have GtkLabels packed inside some vboxes or tables, the width of the box is 
determined by the size of some other elements (buttons, listviews, ...).
when the text inside the labels is changed, and this text is too long to fit, 
the box automatically resizes, which distorts the whole window layout and 
pushes some widgets "off the screen".
so how can I fix the width of the GtkLabel (which I don't know at creation), 
and let the text automatically wrap or scroll, if it doesn't fit?